In comparison to general fibers for medical use, the conventional medical spandex fibers display stronger adhesion to make fibers stick together. This contributes to poor unwindability, resulting in many breaks of the filaments in the post-process such as covering, warping, knitting, etc., and causes generation of static electricity to make the tension of the fiber non-uniform. Generally, in an attempt to improve this problem, an anti-adhesive is added to the polymer to enhance the characteristics of the polymer.
However, it is reported as a possible problem pertaining to the addition of the anti-adhesive used to lower the adhesion that the spandex fiber for use in the manufacture of diapers is susceptible to a slip-causing deterioration in the adhesion, by means of a hot melt adhesive, between the spandex fiber and a polypropylene nonwoven fabric or a polypropylene film during the diaper-manufacturing process, thereby making it difficult to adhere the spandex fiber properly in the diaper and maintain the shape of the diaper.
For enhancing the adhesion with the hot melt adhesive, an adhesion enhancer is used in an emulsion, or a thermoplastic polyurethane or a rosin-based compound is added to the polymer, in the production of the spandex fiber. But, when the adhesion enhancer is added to the emulsion, its non-uniform distribution in the emulsion may result in an uneven coating on the surface of the fiber. Further, the use of the thermoplastic polyurethane in the polymer has no effect to enhance the adhesion, and the addition of the rosin-based compound in the polymer increases the unwinding fiber tension of the spandex fiber and results in poor unwindability. It is therefore suggested to solve the problem concerning the deterioration in the adhesion by using a hydrocarbon-based resin monomer or polymer, or its derivatives, capable of enhancing the adhesive characteristics without causing a problem with the unwinding fiber tension, in the polymer.